(1) Field of the Invention
The present invention relates to a novel .delta.-valerolactone ring-containing, optically active compound, which is valuable as a ferroelectric liquid crystal or an additive to a ferroelectric liquid crystal, and a liquid crystal composition comprising this optically active compound.
(2) Description of the Related Art
The mesophase of the liquid crystals currently widely used in a light-receiving type display belongs to the nematic phase, and therefore, the display is characterized in that it does not cause eye fatigue and consumes very little energy. However, this type of display has problems in that the response speed is low and the display cannot be seen from a certain angle.
A display device or printer head using a ferroelectric liquid crystal having a much higher response speed and contrast than those of a nematic liquid crystal has been investigated.
A ferroelectric liquid crystal was discovered for the first time by R. B. Meyer et al in 1975 [J. Physique, 36, L-69-71 (1975)]. This ferroelectric liquid crystal belongs to the chiral smectic C phase (hereinafter referred to as "Sm*C phase"), and a typical compound of this ferroelectric liquid crystal is p-decyloxybenzylidene-p'-amino-2-methylbutyl cinnamate (hereinafter referred to as "DOBAMBC") represented by the following formula (2): ##STR7##
In addition to DOBMBC, the ferroelectric liquid crystal materials prepared to date have a problem in that the temperature range showing the ferroelectric characteristics (the temperature range wherein the Sm*C phase is present) is narrow, and therefore, attempts have been made to expand the temperature range showing the Sm*C phase to the lower and higher temperature sides, taking room temperature as the center, by mixing several ferroelectric liquid crystals. Accordingly, the development of a ferroelectric liquid crystal having the Sm*C phase present in a practical temperature range is desired, and further, a ferroelectric crystal having a larger spontaneous polarization than that of the known ferroelectric liquid crystals is desired as a liquid crystal for a printer head for which an ultra-high response speed is required.